The public hearing is not a part of the EIA which refers to Environmental Impact Assessment.
For a big project in Thailand, both a public hearing and EIA have to be performed because they are required by Thai Law.
The public hearing is a process where the authorities have to give an opportunity for local people living where the project will be situated to express their views whether pro or con, regarding the project.
Some projects, even if the opinions of the local people are against, the projects will still carry on if they can be proved to be more beneficial to the public.
Nonetheless, in some cases, there are disputes between the authorities and the local people heard in the Administrative Court with regard to certain project.